1. Field of Invention
The invention relates to an electrophotographic image forming apparatus such as a laser printer.
2. Description of Related Art
Laser printers typically include a process cartridge containing a photosensitive drum, a scorotron charger disposed facing the photosensitive drum, and a developing device. Such a process cartridge can also be attached to and removed from a casing. The scorotron charger is provided with a wire for discharging electricity that is disposed along a rotation axis of the photosensitive drum and a cleaning unit for removing foreign materials such as dust adhered to the wire. A cleaning unit is provided such that it is slidable along the length of the wire while holding the wire. The process cartridge is removed from the casing and the cleaning unit is manually moved along the length of the wire, so that the wire is cleaned.
Japanese Laid-Open Patent Publication No. 8-6464 discloses an apparatus where a process cartridge is attached to and removed form a casing in a direction parallel to the longitudinal direction of a wire, that is, the axis of a photosensitive drum. At the time of attachment or removal of the process unit, an actuator held in the casing is engaged with a cleaning unit and the cleaning unit slides on the wire concurrently with the attachment or removal of the process unit, thereby dust adhered to the wire is cleaned.
However, in the above method, as the process cartridge is removed from the casing parallel to the axis of the photosensitive drum, a bearing that supports one end of a support shaft of the photosensitive drum is provided in a cover that opens and closes at the time of attachment and removal of the process cartridge. For this structure, the positioning accuracy of the photosensitive drum cannot be obtained, which may lead to a loss of image quality.